The
concept of unaltered remains can refer to multiple modes
of preservation. Freezing, encapsulation in amber (tree resin),
desiccation, and chemical preservation, such as entombment
in petroleum containing sediment, are examples explored in
our museum. The term unaltered remains is a bit misleading.
It does not mean that the organism is unchanged. Nucleic
acids (DNA and RNA), proteins, pigments, and soft tissues
may be degraded. Tissues, if present, have usually lost water.
However, organic matter that is present has not changed into
another substance.

Freezing, mummification
(desiccation), oil seeps, and amber can preserve both soft
and hard tissues. Sometimes the soft tissues decay, but
the hard parts remain unaltered. Teeth, bones, and shells
may be preserved in this way. Forty thousand year old bones
encased in the asphalt of Rancho La Brea in Los Angeles
retain their original composition. Mollusk shells of the
Pleistocene are known that retain their mother-of-pearl
aragonite layer. Even some Cretaceous aged mollusks are
found with their aragonite intact (Prothero, 2004, p. 9).

The
mammoth tooth pictured on this page retains original enamel,
dentine, and bone. Unaltered teeth, bones,
and shells may also exhibit
some signs of permineralization with calcium phosphate, pyrite
or other minerals.